Wireless transceiver management system and method

TECHNICAL FIELD

p-0002This invention relates to wireless security and alarm systems, and in particular to a system and method for managing data communications between wireless security system devices and multiple wireless transceivers.

BACKGROUND ART

p-0003Security systems such as alarm systems often utilize wireless transmissions to and from devices such as motion detectors, keypads, door and window contacts, etc. The wireless devices communicate with a control panel (the device that controls the operation of the security system) via a series of strategically located wireless transceivers. The wireless transceivers have wireless receiving capabilities to receive transmissions from various wireless devices, and they have wireless transmission capabilities to send transmissions to various wireless devices. The wireless transceivers are interconnected to the control panel via a wired connection, such as an RS-485 wired connection.

p-0004In many security systems, a number of wireless transceivers will be strategically located in locations throughout the premises being protected. Once these transceivers are installed they are usually not moved again, since they are wired to the control panel and the cost of rewiring is prohibitive. The wireless security system devices are then installed as desired throughout the premises. Many of the wireless security system devices will be installed in fixed locations; some, however, are mobile devices (e.g. fobs) that may be carried throughout the premises by a user.

p-0005An important parameter in the operation of these wireless security systems is the communications between the devices and the transceivers, which in turn communicate with the control panel. Several problems may occur in this regard.

p-0006<figref idrefs="DRAWINGS">FIG. 1</figref> illustrates a wireless coverage diagram, where transceivers <b>6</b><i>a</i>, <b>6</b><i>b</i>, and <b>6</b><i>c </i>are located in a premises and wired to a control panel <b>4</b>. Various wireless security devices are shown by the black dots. Transceiver <b>6</b><i>a </i>provides coverage area <b>7</b>, transceiver <b>6</b><i>b </i>provides coverage area <b>11</b>, and transceiver <b>6</b><i>c </i>provides coverage area <b>13</b>. Overlap is provided to ensure all desired areas of the premises are covered. Device <b>8</b> is within range of transceiver <b>6</b><i>a</i>, but device <b>8</b><i>a </i>is within range of both transceivers <b>6</b><i>a </i>and <b>6</b><i>b. </i>

p-0007When a device sends an RF transmission to a given transceiver, it will expect to receive an acknowledge message (ACK) in return. In addition, the control panel may need to send data signals to a certain device via a transceiver. Since a given wireless device may be in range of several transceivers as shown in <figref idrefs="DRAWINGS">FIG. 1</figref>, it is desired that only one transceiver send RF transmissions to that device at any time in order to avoid message collisions. Thus, even though several transceivers may receive RF transmissions from a device, it is desired that only one of those transceivers issue an ACK to that device. Preferably the device would receive transmissions from the transceiver with the best transmission parameters (i.e. the strongest signal with respect to that device).

p-0008Conditions may change that cause a desire to change the device-transceiver pairing assignment, such as if furniture is moved, etc. In that case it would be desired to reallocate the device-transceiver pairing assignment accordingly.

p-0009In addition, movable devices such as fobs will come into and out of range with different transceivers as the fob is transported throughout the premises.

p-0010Thus, it is desired to provide a wireless security system in which transceivers are dynamically allocated to fixed location bi-directional wireless devices in order to optimize data transmissions therebetween.

p-0011It is also desired to provide such a wireless system that optimizes transmissions between movable bi-directional fobs and fixed location transceivers.

DISCLOSURE OF THE INVENTION

p-0012The present invention in a first aspect is a method of managing data communications in a wireless security system. A wireless message is transmitted from a wireless security device and then received by at least two wireless transceivers. Each wireless transceiver that receives the wireless message then analyzes the received wireless message to generate received signal strength indication data. A digital data message is then sent via a wired connection such as a data bus to a control panel, the digital data message including at least some data from the received wireless message and the received signal strength indication data. The control panel receives each digital data message sent from the wireless transceivers and then analyzes the received signal strength indication data from each received digital data message to determine which wireless transceiver generated the highest received signal strength indication data. The control panel then designates data exchange responsibility to the wireless transceiver determined to have generated the highest received signal strength indication data. The control panel indicates to the wireless transceiver determined to have generated the highest received signal strength indication data that the wireless transceiver has been designated with data exchange responsibility with the wireless security device.

p-0013Only the designated wireless transceiver will transmit an acknowledgement message to that wireless security device. Further, subsequent wireless messages from the wireless security system device will be acknowledged only by that designated wireless transceiver.

p-0014While the first aspect of the invention described above is generally implemented using fixed location wireless security devices (such as PIRs or door contact switches), a second aspect of the invention applies to portable wireless security devices such as fobs. A wireless message is transmitted from a portable wireless security device and then received by a plurality of wireless transceivers. A digital data message is then sent via a wired connection such as a data bus to a control panel, the digital data message including at least some data from the received wireless message. Note that received signal strength indication data is not implemented in this aspect of the invention. The control panel receives each digital data message sent from the wireless transceivers and then determines which wireless transceiver was the first wireless transceiver to have sent the digital data message. The control panel then designates data exchange responsibility to the wireless transceiver determined to have been the first wireless transceiver to have sent the digital data message. The control panel indicates to the wireless transceiver determined to have been the first wireless transceiver to have sent the digital data message that the wireless transceiver has been designated with data exchange responsibility with the wireless security device.

p-0015A timeout clock may be initiated such that when the timeout clock reaches a predetermined time, then the control panel indicates to the designated wireless transceiver that the designated wireless transceiver no longer has been designated with data exchange responsibility with the wireless security device. Alternatively, a message counter may be implemented, which is incremented for each time a message is received from a portable wireless security device. When the message counter reaches a predetermined count, then the control panel indicates to the designated wireless transceiver that the designated wireless transceiver no longer has been designated with data exchange responsibility with the wireless security device.

BRIEF DESCRIPTION OF THE DRAWING

p-0016<figref idrefs="DRAWINGS">FIG. 1</figref> is an illustration of the typical coverage areas of the wireless security system of the present invention.

p-0017<figref idrefs="DRAWINGS">FIG. 2</figref> is a block diagram of the wireless security system of the present invention.

p-0018<figref idrefs="DRAWINGS">FIG. 3</figref> is a block diagram of a wireless security device of the present invention.

p-0019<figref idrefs="DRAWINGS">FIG. 4</figref> is a block diagram of a wireless transceiver of the present invention.

p-0020<figref idrefs="DRAWINGS">FIG. 5</figref> is a block diagram of the control panel of the present invention.

p-0021<figref idrefs="DRAWINGS">FIGS. 6</figref><i>a </i>and <b>6</b><i>b </i>are a flowchart of the operation of a first aspect of the present invention used with fixed location security devices.

p-0022<figref idrefs="DRAWINGS">FIGS. 7</figref><i>a </i>and <b>7</b><i>b </i>are a flowchart of the operation of a second aspect of the present invention used with portable security devices.

BEST MODE FOR CARRYING OUT THE INVENTION

p-0023The preferred embodiments of the present invention will now be described with respect to the Figures. <figref idrefs="DRAWINGS">FIGS. 1 and 2</figref> illustrates a top level block diagram of a first aspect of the present invention. The security system <b>2</b> includes at least one, and likely many, wireless security devices <b>8</b>. These wireless security devices <b>8</b> are known in the art, and include (as shown in <figref idrefs="DRAWINGS">FIG. 3</figref>) a sensor <b>30</b>, processing circuitry <b>32</b>, a wireless (e.g. RF) transmitter <b>36</b>, and a wireless receiver <b>34</b>. The sensor <b>30</b> is a generic representation of one or more of many types of devices such as passive infrared detectors (PIRs), microwave oscillators, door or window contact switches, glass break detectors, etc. Processing circuitry interoperates with the sensor <b>30</b> to generate a wireless message for transmission via the transmitter to the rest of the security system <b>2</b> as well known in the art, and may include device status, tamper status, battery status, etc. The receiver <b>34</b> enables the security device <b>8</b> to operate as a two-way device and receive messages from the system <b>2</b>, including message acknowledgement messages (ACK), request for status messages, etc.

p-0024In this first aspect of the invention, the wireless security device <b>8</b> will be a fixed location device such as a PIR or door contact switch. These devices are mounted by an installer and generally not moved from the installed location. In a second aspect of the invention described below, the security device is portable, such as a fob that is carried by a user and used to control certain aspects of the system. Portable wireless security devices present unique problems that are addressed by the second aspect of the invention below.

p-0025Also shown in <figref idrefs="DRAWINGS">FIG. 2</figref> are a plurality of wireless transceivers <b>6</b><i>a</i>, <b>6</b><i>b</i>, <b>6</b><i>c</i>, which are referred to generally as transceiver <b>6</b> for purposes of clarity. The transceivers <b>6</b> are strategically located throughout the premises based on the coverage desired; i.e. based on the locations of the wireless security devices <b>8</b> with which they will communicate. For example, a building with four floors and four wings on each floor may have one transceiver in each wing on each floor, resulting in sixteen transceivers. As security devices <b>8</b> are added to the system they will communicate and interoperate with the transceivers <b>6</b> as further described herein.

p-0026<figref idrefs="DRAWINGS">FIG. 2</figref> also illustrates a control panel <b>4</b> that is hardwired to each of the transceivers <b>6</b> via a bus <b>12</b>. In the preferred embodiment an RS-485 wired bus is used, although many other types may be implemented in accordance with the desires of the system designer. <figref idrefs="DRAWINGS">FIG. 4</figref> illustrates a wireless transceiver <b>6</b> that includes a receiver <b>40</b> for receiving messages transmitted by the wireless security devices <b>8</b>, and a transmitter <b>42</b> for transmitting messages such as ACK back to the security device <b>8</b>. The transceiver <b>6</b> also has processing circuitry <b>44</b>, a received signal strength indication (RSSI) measurement circuit <b>46</b>, memory <b>48</b>, and a bi-directional bus interface <b>49</b> which can communicate over the bus <b>12</b> with the control panel via digital data messages. In the preferred embodiment, these digital data messages are sent via the RS-485 protocol that is well known in the art.

p-0027RSSI measurement techniques are also well known in the art. For example, U.S. Pat. No. 5,801,626, ALARM COMMUNICATIONS SYSTEM WITH SUPERVISION SIGNAL RSSI ANALYSIS, assigned to the same assignee as the present application, which is incorporated by reference herein, describes such an RSSI measurement circuit. This is an example only of such a circuit and the operation of the present invention is not limited to the use of that circuit.

p-0028<figref idrefs="DRAWINGS">FIG. 5</figref> also illustrates the control panel <b>4</b>. Control panels used in security and alarm system are well known in the art, and only the aspects of such a device relevant to the present invention are illustrated and discussed herein. Thus, the control panel <b>4</b> includes a bi-directional bus interface <b>50</b> that can communicate over the bus <b>12</b> with the transceivers <b>6</b> via digital data messages. The control panel <b>4</b> also has processing circuitry <b>52</b> and a memory <b>54</b> that stores a transceiver allocation table as further described below.

p-0029Reference is now made to the flowchart of <figref idrefs="DRAWINGS">FIGS. 6</figref><i>a </i>and <b>6</b><i>b </i>to describe the operation of this first aspect of the invention. A first wireless security device is referred to generally as WSDx, where x=1, 2, 3 . . . . An installer affixes WSDx in the desired location, such as a PIR being installed in an upper corner of a room. The installer causes WSDx to transmit a wireless message (for example by initiating a tamper detection switch as known in the art). The wireless message from WSDx is transmitted (step <b>602</b>) and received by several wireless transceivers. In this example the wireless message will be received by only two transceivers TCVR<b>1</b> (step <b>604</b>) and TCVR<b>2</b> (step <b>606</b>), but any number of transceivers would be included if they are in range and the wireless message reaches them. Each transceiver will then analyze the wireless message from WSDx and generate an RSSI signal as known in the art. Thus, TCVR<b>1</b> will generate RSSIx<b>1</b> at step <b>608</b>, and TCVR<b>2</b> will generate RSSIx<b>2</b> at step <b>610</b>. Then, each transceiver will assemble a digital data message that includes data DATAx received from the WSDx (i.e. after demodulation) as well as the measured RSSI data. Thus, TCVR<b>1</b> will send message MSGx<b>1</b> (DATAx, RSSIx<b>1</b>) onto the bus <b>12</b> at step <b>612</b>, and TCVR<b>2</b> will send message MSGx<b>2</b> (DATAx, RSSIx<b>2</b>) onto the bus <b>12</b> at step <b>614</b>.

p-0030The control panel <b>4</b> will receive MSGx<b>1</b> and MSGx<b>2</b> (step <b>616</b>) and process them as follows. Processing circuitry <b>52</b> of the control panel <b>4</b> will analyze the RSSI data from MSGx<b>1</b> (RSSx<b>1</b>) and from MSGx<b>2</b> (RSSIx<b>2</b>), and determine at step <b>618</b> which RSSI data is greater (or greatest if more than two transceivers send RSSI data). Assuming for sake of explanation that MSGx<b>1</b> has the greater RSSIx, (step <b>620</b>), then the control panel <b>4</b> will designate that TCVR<b>1</b> will have primary data exchange responsibility with WSDx (step <b>622</b>). The control panel will store this designation information in the transceiver allocation table <b>54</b> and send a data message to TCVR<b>1</b> (step <b>624</b>) to instruct TCVR<b>1</b> that it must send an acknowledgement message (ACK) to the WSDx (step <b>626</b>) and continue to acknowledge subsequent messages from WSDx until otherwise notified by the control panel. The TCVR<b>1</b> will set a flag in its memory to indicate its status as primary acknowledging transceiver and cause it to acknowledge immediately when it receives a subsequent message from WSDx (steps <b>628</b>, <b>630</b>, <b>632</b>).

p-0031In addition, since TCVR<b>1</b> has the optimal data transfer characteristics with WSDx, any subsequent data messages that must be sent to WSDx will be sent by the control panel via TCVR<b>1</b>. For example, if the control panel requires a status message from WSDx, it will send a status request message to TCVR<b>1</b> to forward on to WSDx.

p-0032Certain events may occur that could cause the designated transceiver to no longer have the highest RSSI from a given wireless security device. For example, a transceiver device may fail. In addition, furniture may be moved in the premises that could change the RF signal transmission characteristics of the wireless security device/transceiver pair. Thus, the present invention may be configured to adapt to compensate for these types of changing conditions. In order to do this, each transceiver that receives a wireless message from a wireless security device will continue to generate RSSI data and send it to the control panel, even though that transceiver may not have primary data exchange responsibility with that wireless security device. Even though it forwards the RSSI data and message data to the control panel every time it receives a transmission from a security device, it will not ACK that security device unless it has its flag set in memory as described above.

p-0033Since the control panel may constantly receive digital data messages from all receivers in range of a given security device, it can continue to monitor the relative RSSI values and ascertain if the primary data exchange responsibility should change from the previously assigned transceiver to a different one. This may be done in various ways. For example, the control panel may be programmed to re-evaluate RSSI measurements periodically, for example once every hour or once every day, etc. Or, it may take a moving average of a certain number of signals. Or, it may check the RSSI signals every 100^thmessage received, etc. The parameters of modifying data exchange responsibilities may be set by the system designer to ensure reliability in any of these or other manners. Likewise, the control panel may determine that a given transceiver has stopped responding and re-assign data exchange responsibility to a different transceiver accordingly. By storing historical RSSI data in the table <b>54</b>, decisions on re-assigning data exchange responsibilities are more readily made. Table <b>54</b> also contains mapping assignment data that keeps track of which transceiver has been paired with which security device.

p-0034As described above, in the situation where the transceiver no longer is in communication with the control panel, the control panel will reallocate data transfer responsibility (e.g. ACK) to another transceiver. When this is due to a complete failure of the first transceiver, then that first transceiver will of course stop ACKing since it is dead. However, in the case that the transceiver is still able to communicate with the transceiver even though its communication with the control panel has failed, it is also desired for that transceiver to stop communicating to the security device on its own (i.e. without requiring a termination message from the control panel). This is important to avoid multiple transceivers from ACKing the security device (and avoid collisions). Thus, the transceiver will be programmed with a timeout feature that will cause it to clear its ACK flag if it has been unable to communicate successfully with the control panel after a certain time (e.g. 1 minute).

p-0035Thus, as shown in <figref idrefs="DRAWINGS">FIG. 6</figref><i>a</i>, the control panel may determine at a subsequent time that MSGx<b>2</b> now has a higher RSSI value than MSGx<b>1</b> (step <b>634</b>). In this case, the control panel reallocates primary data exchange responsibility to TCVR<b>2</b> rather than TCVR<b>1</b> (step <b>636</b>). To do this, the control panel sends an allocation message to TCVR<b>2</b> (step <b>638</b>) and a termination message to TCVR<b>1</b> (step <b>640</b>). From then on, acknowledgement responsibility will be carried out by TCVR<b>2</b> for WSDx (step <b>642</b>).

p-0036In addition, the control panel may be overridden by a user input, such as by entry via a keypad, to assign a predefined transceiver to a given wireless security device, regardless of the RSSI signal measurement described above.

p-0037While the first aspect of the invention described above is generally implemented using fixed location wireless security devices (such as PIRs or door contact switches), a second aspect of the invention applies to portable wireless security devices such as fobs. As shown in <figref idrefs="DRAWINGS">FIG. 3</figref>, these portable wireless security devices <b>8</b> may also have inputs <b>33</b> such as buttons that may be pressed by a user to execute certain system function such as arm or disarm, etc., as well known in the art.

p-0038Reference is now made to the flowchart of <figref idrefs="DRAWINGS">FIGS. 7</figref><i>a </i>and <b>7</b><i>b </i>to describe the operation of this second aspect of the invention. As in <figref idrefs="DRAWINGS">FIG. 6</figref>, a first portable wireless security device is referred to generally as WSDy, where y=1, 2, 3 . . . . The installer causes WSDy to transmit a wireless message (for example by pressing an input button <b>33</b>). The wireless message from WSDy is transmitted (step <b>702</b>) and received by several wireless transceivers. In this example the wireless message will be received by only two transceivers TCVR<b>1</b> (step <b>704</b>) and TCVR<b>2</b> (step <b>706</b>), but any number of transceivers would be included if they are in range and the wireless message reaches them. Note that received signal strength indication measurement is not implemented in this aspect of the invention. Each transceiver will assemble a digital data message that includes data DATAy received from the WSDy (i.e. after demodulation). Thus, TCVR<b>1</b> will send message MSGy<b>1</b> onto the bus <b>12</b> at step <b>712</b>, and TCVR<b>2</b> will send message MSGy<b>2</b> onto the bus <b>12</b> at step <b>714</b>.

p-0039The control panel <b>4</b> will receive MSGy<b>1</b> and MSGy<b>2</b> (step <b>716</b>) and process them as follows. Processing circuitry <b>52</b> of the control panel <b>4</b> will determine at step <b>718</b> which message was received first (either MSGy<b>1</b> or MSGy<b>2</b>) at step <b>718</b>. Assuming for sake of explanation that MSGy<b>1</b> was received first (step <b>720</b>), then the control panel <b>4</b> will designate that TCVR<b>1</b> will have primary data exchange responsibility with WSDy (step <b>722</b>). The control panel will store this designation information in the transceiver allocation table <b>54</b> and send a data message to TCVR<b>1</b> (step <b>724</b>) to instruct TCVR<b>1</b> that it must send an acknowledgement message (ACK) to the WSDy (step <b>726</b>) and continue to acknowledge subsequent messages from WSDy until otherwise notified by the control panel. The TCVR<b>1</b> will set a flag in its memory to indicate its status as primary acknowledging transceiver and cause it to acknowledge immediately when it receives a subsequent message from WSDy (steps <b>728</b>, <b>730</b>, <b>732</b>).

p-0040In addition, any subsequent data messages that must be sent to WSDy will be sent by the control panel via TCVR<b>1</b>. For example, if the control panel requires a status message from WSDy, it will send a status request message to TCVR<b>1</b> to forward on to WSDy.

p-0041Since in this embodiment the wireless security device is portable rather than fixed in a single location, it is more likely that the allocation of data exchange responsibility will change from one transceiver to another. This may be done in one or more of several possible ways. Generally speaking, a reallocation sequence will be initiated at some point by the control panel (step <b>734</b>). Once this process occurs and the decision to reallocate is made, then the control panel reallocates primary data exchange responsibility to TCVR<b>2</b> rather than TCVR<b>1</b> (step <b>736</b>). To do this, the control panel sends an allocation message to TCVR<b>2</b> (step <b>738</b>) and a termination message to TCVR<b>1</b> (step <b>740</b>). From then on, acknowledgement responsibility will be carried out by TCVR<b>2</b> for WSDy (step <b>742</b>). This process is of course repeated periodically.

p-0042For example, the reallocation process may implement the use of a timeout clock <b>53</b> in control panel <b>4</b>. When the timeout clock <b>53</b> reaches a predetermined time (e.g. 12 seconds), then the control panel <b>4</b> indicates to the designated wireless transceiver TCVR<b>1</b> that it longer has been designated with data exchange responsibility with the wireless security device WSDy (step <b>738</b>). Alternatively, a message counter may be implemented by the control panel <b>4</b>, which is incremented for each time a message MSGy is received from the portable wireless security device WSDy. When the message counter reaches a predetermined count, then the control panel <b>4</b> indicates to the designated wireless transceiver TCVR<b>1</b> that it no longer has been designated with data exchange responsibility with the wireless security device WSDy (step <b>738</b>). Likewise, data exchange responsibility may be modified if the control panel receives messages from a portable wireless security device via a different transceiver but does not receive it from the designated transceiver (indicating that the portable device was likely carried out of range of the designated transceiver).

p-0043It will be apparent to those skilled in the art that modifications to the specific embodiment described herein may be made while still being within the spirit and scope of the present invention.